How to get vorticough achievement?(Half life 2)

/ info english/ In the video shown where you can earn this achievement , there is all this after defeating helicopter hunter , enjoy.
/ info russia/  âèäåî ïîêàçàíî ãäå ìîæíî çàðàáîòàòü ýòî äîñòèæåíèå, ïðîèñõîäèò âñå ýòî ïîñëå ïîáåäû íàä âåðòîëåòîì îõîòíèêîì, ïðèÿòíîãî ïðîñìîòðà.˜˜˜˜˜˜˜ dle 10.6˜˜˜˜˜˜ ˜˜˜˜˜˜˜˜˜